Hi Dave, my old marine tank was roughly the same size and from memory I think it went just over 1 Ton when fully loaded with all the coral sand and living rock.
Hope you have that floor well strengthened, hate to here the people below you getting a free shower.

I made mine myself. All held together with silicone (Dow Corning). It realy makes certain muscles sqeak when filling it up. I was getting ready to do a runner before the other half got home if the glass went. .